1. Field of the Invention
The present invention generally relates to computer systems, particularly to a method of upgrading or servicing computer components, and more specifically to a method of exchanging (swapping out) voltage regulator modules for a computer system, without powering down the computer system or otherwise interrupting service.
2. Description of Related Art
Modern computing systems are often constructed from a number of processing units and a main memory, connected by a generalized interconnect. The basic structure of a conventional multi-processor computer system 10 is shown in FIG. 1. Computer system 10 has several processing units (CPUs) 12a, 12b, and 12c which are connected to various peripheral, or input/output (I/O) devices 14 (such as a display monitor, keyboard, and permanent storage device), memory device 16 (random-access memory or RAM) that is used by the processing units to carry out program instructions, and firmware 18 whose primary purpose is to seek out and load an operating system from one of the peripherals (usually the permanent memory device) whenever the computer is first turned on.
Processing units 12a-12c communicate with the peripheral devices, memory and firmware by various means, including a bus 20. Computer system 10 may have many additional components which are not shown, such as serial and parallel ports for connection to, e.g., modems or printers. Those skilled in the art will further appreciate that there are other components that might be used in with those shown in the block diagram of FIG. 1; for example, a display adapter might be used to control a video-display monitor, a memory controller can be used to access memory 16, etc. The computer can also have more than three processing units. In a symmetric multi-processor (SMP) computer, all of the processing units 12a-12c are generally identical, that is, they all use a common set or subset of instructions and protocols to operate, and generally have the same architecture.
Conventional computer systems often allow the user to add various components after delivery from the factory. For peripheral devices, this can be accomplished using an xe2x80x9cexpansionxe2x80x9d bus, such as the Industry Standard Architecture (ISA) bus or the Peripheral Component Interconnect (PCI) bus. Another component that is commonly added by the user is main memory. This memory is often made up of a plurality of memory modules that can be added or removed as desired. Even processing units can be added or swapped out, in more recent computer designs.
One item that heretofore has not been user-serviceable is the voltage regulator module that is used for the various computer components. These components require different power sources/references at precise voltages, and the voltage regulator module (VRM) produces these voltages. A VRM is connected to the main power supply for the computer (e.g., a 110 volt AC wall outlet), and uses transformers and solid-state circuitry to generate smooth reference signals which are essentially invariant over a reasonable range of operating parameters (e.g., temperature).
If a VRM is defective and the computer system is powered-up, the system will simply not pass the power-on test (POST), and will halt operation. However, if a system is running and the VRM becomes defective, it can wreak havoc on the system. In order to replace a defective VRM, it is necessary to power down the computer system, since VRMs are integrated (hard-wired) into the system hardware. A field service engineer often must be called to perform the maintenance.
For many computer systems (particularly large servers used in a client-server network), there may be hundreds of users connected to it, and the down time required to perform a VRM service operation can be extremely expensive. Also, in systems which are used in mission-critical applications, it is highly desirable to be able to perform a VRM service operation without service interruption, particularly when it is necessary to replace a defective VRM.
Some computer components, such as xe2x80x9chot-pluggablexe2x80x9d PCI adapters, are currently available that can be added or removed from a computer system while the system is fully operational. Each PCI adapter slot has a separate power line, a separate reset line, and a switch connecting the slot to the PCI bus, allowing the slot to be electrically isolated from the PCI bus, and reactivated after insertion of a new PCI device into the slot. This hot-plug capability has never been expanded to VRMs.
A user may not only want to service a defective VRM without service interruption, but may also desire to add more power capacity to an existing system (in order to supply new, added components), again without service interruption. It would, therefore, be desirable to provide a method of upgrading or servicing a system""s voltage regulator module without requiring a powering down or interruption of the system. It would be further advantageous if the method did not require the expertise of a field service engineer to carry out the maintenance.
It is therefore one object of the present invention to provide an improved method of upgrading and servicing components of a computer system.
It is another object of the present invention to provide such a method that allows a voltage regulator module (VRM) of the computer system to be upgraded or serviced, without interrupting system operation.
It is yet another object of the present invention to provide such a method that does not require the VRM to be hard-wired to the system, so as to simplify any VRM maintenance.
The foregoing objects are achieved in a power subsystem for a computer system, generally comprising a circuit board having at least one voltage rail for supplying power to a component of the computer system, and means for connecting a plurality of voltage regulator modules (VRMs) to the voltage rail, while limiting disturbances on the voltage rail when a VRM is electrically connected thereto. The circuit board may be, e.g., a system board of the computer system having firmware mounted thereon. The disturbances on the voltage rail can be prevented by charging the voltage output of the VRM prior to directly connecting the voltage output to the voltage rail.
In an illustrative embodiment, each VRM has a DC/DC circuit and a VRM connector having a plurality of pins electrically connected to respective connections of the DC/DC circuit. The pins include at least one ground pin, and charge pins coupled to respective capacitors and to voltage outputs of the DC/DC circuit. A voltage input pin is connected to a voltage input of the DC/DC circuit, and voltage output pins are connected respectively to the voltage outputs of the DC/DC circuit. The voltage output pins are shorter than the charge pins and shorter than the ground pin such that, as the connector is mated with a corresponding connector on the system board, the capacitors are first charged via resistive paths connected to the voltage rails, prior to directly connecting the voltage outputs to the voltage rails. In the manner, the VRMs become xe2x80x9chot-pluggable,xe2x80x9d enabling a user to upgrade or service the system while it is still running, with little or practically no effect on service.
The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description.